WASHINGTON 
Democrats pounced on Mitt Romney's selection of Wisconsin Rep. Paul Ryan as his running mate Saturday, saying the pick showed a commitment to "budget-busting tax cuts" for the wealthy and greater burdens on the middle class and seniors.

President Barack Obama's campaign team said Romney's choice made clear that the former Massachusetts governor would be forced to adhere to the principles laid out in the House Republican budget - authored by Ryan - which they said would undermine entitlement programs crucial to middle-class families and seniors. Democrats said privately that the choice of Ryan could help Obama in states with large numbers of elderly voters, such as Florida, Pennsylvania and Ohio.

Obama's campaign manager, Jim Messina, said in a statement that Romney had "chosen a leader of the House Republicans who shares his commitment to the flawed theory that new budget-busting tax cuts for the wealthy, while placing greater burdens on the middle class and seniors, will somehow deliver a stronger economy."

Previewing the campaign's line of attack, Messina called Ryan the "architect of the radical Republican House budget" and said it would "end Medicare as we know it by turning it into a voucher system, shifting thousands of dollars in health care costs to seniors." Ryan was chief author of a House-backed budget plan that would curb overall entitlement spending and convert Medicare into a voucher-like system in which future seniors would receive subsidies to purchase health insurance on the open market.

Less than two hours after Romney introduced Ryan as his running mate, the Obama campaign released a 90-second Web video showing footage of the men appearing together. The ad calls Ryan the "mastermind behind the extreme GOP budget plan" and includes an audio clip of Romney saying earlier this year that it would be "marvelous" if the Senate were to adopt the Ryan budget. The ad ends with this tagline: "Mitt Romney and Paul Ryan: Back to the failed top-down policies that crashed our economy."

Democratic National Committee Chair Debbie Wasserman Schultz of Florida said Ryan had laid the groundwork in Congress for Romney's budget plan, which she said gives tax cuts to millionaires while punishing middle-class families. She said Romney and Ryan would repeat mistakes of former President George W. Bush.

"A Romney-Ryan ticket is sure to take us back and repeat the same catastrophic mistakes that got us into the mess we found ourselves in in the first place," Wasserman Schultz said in a statement.

Senate Majority Leader Harry Reid, who has blasted Romney for failing to release additional years of his tax returns, said in a statement that by picking Ryan, Romney "has doubled down on his commitment to gut Social Security and end Medicare as we know it."

Romney's choice "demonstrates that catering to the tea party and the far-right is more important to him that standing up for the middle class," said Reid, D-Nev.

Obama was traveling to Chicago on Saturday but had no public events planned. He was holding birthday-related fundraisers on Sunday in Chicago, including one at his South Side home, and then taking a three-day swing through Iowa, the state that launched his presidential bid in 2008.